Bring parity to initial() (#2458)

Co-authored-by: ike709 <[email protected]>

Author: ike709

Content.Tests/DMProject/Tests/SpecialProcs/initial/initial_global.dm

@@ -0,0 +1,3 @@
+// COMPILE ERROR OD0011
+/proc/RunTest()
+	initial(global)

Content.Tests/DMProject/Tests/SpecialProcs/initial/initial_proc_args.dm

@@ -9,6 +9,7 @@
 
 	ASSERT(initial(b) == 5)
 	ASSERT(initial(c) == "e")
+	ASSERT(initial(args[2]) == 5)
 
 /proc/RunTest()
 	someargs("3", 5, c = "cc") 

Content.Tests/DMProject/Tests/SpecialProcs/initial/initial_procself.dm

@@ -0,0 +1,3 @@
+/proc/RunTest()
+	. = "foo"
+	ASSERT(initial(.) == "foo")

DMCompiler/DM/Expressions/LValue.cs

@@ -25,10 +25,7 @@ public void EmitPushValueNoConstant(ExpressionContext ctx) {
         ctx.Proc.AddLabel(endLabel);
     }
 
-    public virtual void EmitPushInitial(ExpressionContext ctx) {
-        ctx.Compiler.Emit(WarningCode.BadExpression, Location, $"Can't get initial value of {this}");
-        ctx.Proc.PushNullAndError();
-    }
+    public abstract void EmitPushInitial(ExpressionContext ctx);
 }
 
 /// <summary>
@@ -42,6 +39,11 @@ public override void EmitPushValue(ExpressionContext ctx) {
         ctx.Proc.PushString("Encountered a bad LValue (compiler bug!)");
         ctx.Proc.Throw();
     }
+
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.BadExpression, Location, "Can't get initial value of a bad LValue (compiler bug!)");
+        ctx.Proc.Throw();
+    }
 }
 
 // global
@@ -51,6 +53,11 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         ctx.Compiler.Emit(WarningCode.BadExpression, Location, "attempt to use `global` as a reference");
         return DMReference.Invalid;
     }
+
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.BadExpression, Location, "Can't get initial value of `global`");
+        ctx.Proc.PushNullAndError();
+    }
 }
 
 // src
@@ -62,6 +69,11 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.Src;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on `src` returns the current value");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "src";
 }
 
@@ -75,6 +87,11 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.Usr;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on `usr` returns the current value");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "usr";
 }
 
@@ -85,6 +102,11 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.Args;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on `args` returns the current value");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "args";
 }
 
@@ -95,6 +117,12 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.Callee;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        // This happens silently in BYOND
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on constant var `callee` is pointless");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "callee";
 }
 
@@ -105,6 +133,12 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.Caller;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        // This happens silently in BYOND
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on constant var `caller` is pointless");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "caller";
 }
 
@@ -115,6 +149,12 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         return DMReference.World;
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        // This happens silently in BYOND
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on constant var `world` is pointless");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "world";
 }
 
@@ -162,6 +202,11 @@ public override void EmitPushInitial(ExpressionContext ctx) {
         ctx.Proc.PushReferenceValue(DMReference.Src);
         ctx.Proc.PushString(variable.Name);
         ctx.Proc.Initial();
+
+        if (variable.IsConst) {
+            // This happens silently in BYOND
+            ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on a constant variable is pointless");
+        }
     }
 
     public void EmitPushIsSaved(DMProc proc) {
@@ -220,5 +265,11 @@ public override void EmitPushValue(ExpressionContext ctx) {
         ctx.Proc.PushGlobalVars();
     }
 
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        // This happens silently in BYOND
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on `global.vars` returns the current value");
+        EmitPushValue(ctx);
+    }
+
     public override string GetNameof(ExpressionContext ctx) => "vars";
 }

DMCompiler/DM/Expressions/Procs.cs

@@ -64,6 +64,11 @@ public override DMReference EmitReference(ExpressionContext ctx, string endLabel
         ShortCircuitMode shortCircuitMode = ShortCircuitMode.KeepNull) {
         return DMReference.Self;
     }
+
+    public override void EmitPushInitial(ExpressionContext ctx) {
+        ctx.Compiler.Emit(WarningCode.PointlessBuiltinCall, Location, "calling initial() on `.` returns the current value");
+        EmitPushValue(ctx);
+    }
 }
 
 // ..